Mitch Trubisky has received his first promotion as a professional quarterback. On Wednesday, Bears coach John Fox made the announcement official. Trubisky will be the backup for Sunday's season opener against the Falcons at Soldier Field. And the expectation throughout the organization is that the 23-year-old rookie will handle his jump into the No. 2 role without flinching.

"He earned it," Fox said. "It's not something we handed him for any particular reason other than he earned it."

So there it is, Trubisky's first big step along his path toward becoming the Bears' franchise quarterback. Mike Glennon remains the starter, of course. For now. And the Bears were emphatic Wednesday in expressing their confidence in Glennon, explaining once more that his NFL experience gives him a much more expansive understanding of concepts and coverages and schemes.

General manager Ryan Pace reasserted his belief that Glennon can play at a winning level this season, allowing the organization to take its time with Trubisky.

"He's a very smart, intelligent player," Pace said of Glennon. "There's a lot that went into that evaluation (before signing him). He has a lot of experience that we're leaning on. He was voted a captain for a reason by that locker room. We're ready to watch it unfold."

Still, Trubisky's reward for his productive preseason can't be downplayed. The rookie, from Fox's vantage point, has been impressive in his ability to absorb and process a high volume of information. Offensive coordinator Dowell Loggains, meanwhile, saw situations in every one of the Bears exhibition games in which Trubisky made necessary adjustments on his own. The rookie would check to a running play when the defensive look called for it. He'd detect a blitz coming before the snap and properly adjust the protection.

That growth, Loggains said, wasn't necessarily surprising. "It's just happened faster than anticipated. But he deserves a ton of credit. Because he works his tail off in virtual reality and studying his playbook and watching (film on) his iPad. With all those things, he has earned the spot and put himself in position to be successful."

Even Glennon noticed Trubisky's rapid growth throughout the summer.

"He just had more command and conviction out there," Glennon said. "You could tell. He was more comfortable in the huddle, getting to the line of scrimmage. It takes a little time as a rookie to adjust to that."

Trubisky was not made available to reporters Wednesday and isn't expected to speak until Friday. After last week's exhibition finale against the Browns, however, he expressed confidence in how he'd transition into regular-season mode, a shift that comes with added responsibility.

"I have a pretty good idea of what needs to be done on a weekly basis as far as studying film and body preparation and all of that," Trubisky said. "I'll be ready to roll."

He'll need to be, potentially now just a snap away from making his regular-season debut.

Yet if Glennon stays healthy and excels with his play, keeping Trubisky out of game action for an extended period of time? Loggains stressed the need for Trubisky to keep himself engaged to further his growth.

"Sometimes as a backup you have to have a capacity for boredom," the offensive coordinator said. "You've got to find ways to get extra reps. Is it staying after practice? Is it before practice? Is it doing virtual reality with (quarterbacks coach Dave) Ragone or myself? We've got to find ways. We can't stop the progress that we've had up until this point."

Up to this point, the Bears have done a nice job in fostering their prized rookie's growth. Enough so that they're confident he will be ready to play in an emergency, perhaps as soon as Sunday.

"Obviously, you guys know how we felt about him from the get-go," Pace said. "Every one of these steps has been exciting to see. We just couldn't be happier with his progress."